The present invention relates generally to stent assemblies that are deployed in bifurcated vessels.
While mono-tubular stents have resulted in improved long-term blood flow, stents are associated with severe problems when deployed in a bifurcated lumen, meaning a parent lumen from which a branch vessel splits. It is estimated that 15% to 20% of all stents are deployed at bifurcations.
Treatment of stenotic lesions at bifurcations is associated with increased early complications including compromise of either the branch vessel or the parent vessel and increased potential for restenosis.
One method for stenting a bifurcating vessel includes placing a first stent having a substantially circular side opening in a parent vessel and a second stent having a flared end for stenting the branch vessel.
The first stent is positioned in the lumen of the parent vessel and expanded, after which the second, flared stent is pressed through the side opening of the first stent and expanded in the branch vessel.
One drawback of this method is the difficulty of properly aligning the side opening of the first stent with the branch vessel bifurcation so that the branch vessel stent passes into the branch vessel. Another drawback of this system is that the second, flared, stent is difficult to position properly, and may protrude into the blood stream causing thrombosis.
Another method of treating bifurcations is called the crush method, an example of which is seen in U.S. Patent application 20050049680 (Fischell et al), the entirety of which is hereby incorporated by reference as if fully disclosed herein.
In this method, a first stent is placed into the branch vessel and expanded so that a portion of the stent protrudes into the parent vessel. A second stent is expanded in the parent vessel, crushing the protruding portion of the first stent against the parent vessel wall around the branch vessel opening.
If the first stent is not properly crushed, however, the end of the stent will protrude into the bloodstream, often resulting in thrombosis. Additionally, during crushing, the first stent may pull away from the branch vessel so that there is no support of the branch vessel where support is needed most. Finally, the crush method deposits a large amount of metal at the entrance to the branch vessel lumen, where the tissue is thin and often incapable of supporting the metallic bulk, resulting in restenosis.